A phase retarder is an optical film for realizing a wide view angle of a liquid crystal display, for example. The phase retardation value of the phase retarder depends on a wavelength, and wavelength dispersion of the phase retardation value is largely classified into the following three categories. Namely, the wavelength dispersion of a phase retardation value may be classified into normal dispersion in which the phase retardation value has a larger wavelength dispersion at a shorter wavelength side, flat dispersion in which the phase retardation hardly changes from the short wavelength side to the long wavelength side, and reverse dispersion in which the phase retardation value has smaller wavelength dispersion at a shorter wavelength side. In the case of the phase retarder, it is preferable to show the reverse dispersion because it has a certain phase difference (λ/2, λ/4, and so on) in a wide wavelength band.
However, since most of the phase retarders made of common resin films show the normal dispersion, various kinds of liquid crystal compositions which can provide the reverse wavelength dispersion have been suggested. Commonly, liquid crystal compositions include a rod-type liquid crystal material and a non-liquid crystal material that is aligned perpendicularly to the liquid crystal material. However, the reverse wavelength dispersion is not induced when the mixing ratio of the non-liquid crystal material is low, and the liquid crystal composition loses the liquid crystalline characteristics when the mixing ratio is high. Furthermore, when the content of the non-liquid crystal material is raised for increasing the reverse wavelength dispersion, the birefringence relatively decreases because the reverse wavelength dispersion and the birefringence have complementary characteristics.
Therefore, the developments of materials which can induce strong reverse wavelength dispersion and compositions for optical elements which can induce the reverse wavelength dispersion with a low non-liquid crystal material content are demanded.